1. Field of the Invention
The invention relates to a method for producing a component of a titanium-aluminum base alloy. Furthermore, the invention relates to a component of a titanium-aluminum base alloy, produced with near net shape dimensions.
2. Discussion of Background Information
Titanium-aluminum base alloys in general have a high strength, a low density and good corrosion resistance and are preferably used as components in gas turbines and aircraft engines.
For the above fields of application, in particular alloys with a composition of: aluminum 40 atomic % to 50 atomic %, niobium 3 atomic % to 10 atomic %, molybdenum up to 4 atomic % as well as optionally the elements manganese, boron, silicon, carbon, oxygen and nitrogen in low concentrations as well as titanium as a remainder are of interest.
These alloys preferably solidify completely via the β mixed crystal and pass through a number of phase transformations during a subsequent cooling. A schematic diagram (FIG. 1) shows microstructure formations as a function of the temperature and the aluminum concentration with temperature range data used by one skilled in the art.
The components can be produced by casting a block or by means of powder metallurgy through hot isostatic pressing (HIPing) of alloyed metal powder as well as by casting a block and optionally HIPing of the same with subsequent extrusion molding and respectively with a subsequent forging of the block or intermediate product to form a component, which is subsequently subjected to heat treatments.
Titanium-aluminum materials have only a narrow temperature window for a hot forming, although it can be expanded by the alloying elements niobium and molybdenum, but nevertheless limitations result regarding the deformation or forging of the parts. It is known to produce a component at least in part by non-cutting shaping, by means of slow isothermal deformation, known to one skilled in the art as isothermal forging, but this is associated with high expenditure.
At best, a component produced according to the above technologies will not usually have a homogeneous fine structure because, on the one hand, there is a low and unequal recrystallization potential of the slowly isothermally deformed material, and/or, on the other hand, the diffusion of the atoms of the elements niobium and/or molybdenum requiring a large time expenditure, which are important for a deformability of a material, are aligned according to the forming structure and can thus have a disadvantageous effect on the structure.
Although a homogenization of the microstructure formation and thus the achievement of isotropic mechanical properties of the material through time-consuming annealing treatments is possible on principle, it requires a high expenditure.
For industrial practice, components of a titanium-aluminum base alloy are necessary which have homogeneous mechanical properties independent of direction, wherein the ductility, strength and creep resistance of the material are present in a balanced manner at a high level even at high application temperatures.
It would be advantageous to have available a method with which a component can be produced with homogeneous, fine and uniform microstructure, which component has a balanced ductility, strength and creep resistance of the material in all directions essentially equally at a desired high level and can be produced economically with near net shape dimensions.
It would further be desirable to have available a component which with a targeted phase formation of the microstructure has desired mechanical properties, in particular a yield strength Rp0.2 and a strength Rm as well as total elongation At in the tensile strength test at room temperature and at a temperature of 700° C.